v4.23.1 — the README leads with the document, not the gate

Changed — the README leads with the document, not the gate

The project page still opened with "a deterministic verification layer that
refuses to publish any claim it cannot trace to registered evidence" — the
floor sold as the pitch. Traceability is the price of entry for anything you
put your name on; the reason to use this is the document that comes out.

• New opening: what the tool produces (a submission-ready DOCX aimed at the
  person who grades it, English or Chinese, optionally following your own
  template), with traceability stated plainly as the floor.
• pip install report-workflow moved to the top — it was buried 260 lines
  down and still described PyPI as "once tagged", which shipped this morning.
• New What a graded document reads like: a real rendered discussion
  section, with the derived slope and R² it cites.
• New How it aims at "good", not just "not wrong": reader rubrics,
  structure discipline with its published sources, derived statistics as
  citable evidence.
• "Who is this for" now leads with people handing in documents; the
  fidelity-gate scope note moved down to where the gate is the subject.
• Package description and keywords match the same framing, so the PyPI
  landing page says what the project is for.

Documentation and packaging metadata only; no code change. 463 tests and
both benchmark --checks pass.